Acoustic wave filters and multiplexers using surface acoustic wave resonators have been used for mobile communication terminals. It has been known to use a cancel circuit to improve the attenuation characteristic of the acoustic wave filter and the attenuation characteristic and/or the isolation characteristic of the multiplexer as disclosed in, for example, Japanese Patent Application Publication Nos. 2013-118611 and 2014-120841.
Causing signals passing through a filter and signals passing through a cancel circuit to have opposite phases and the same amplitude improves the attenuation characteristic and/or the isolation characteristic in the attenuation range. However, the use of the cancel circuit deteriorates the attenuation characteristic in other than the attenuation range.